# The process $\mu^+\mu^-\rightarrow hh$

I am doing some calculations in the Standard Model. I have a question that seems rather simple but makes me think a lot. I want to compute the cross section of the following process at the leading order $$\mu^+\mu^-\rightarrow hh.$$ This can be interesting for a mu-collider. The Feynman diagram I can consider has an intermediate higgs particle decaying into a couple of higgs particles (this vertex exists in the Standard Model) while a $Z^0$ is excluded due to conservation of angular momentum. Is this analysis correct? Otherwise, what is the right Feynman diagram? Also references could be part of a good answer.

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You must also take in account the diagram where a muon is the intermediate state, although it is not dominant. This particle will connect the two Higgs vertices.

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Do you mean a box diagram? –  Jon Mar 26 '14 at 18:13
No, it is a tree level process. You connect $\mu^-$ and $\mu^+$ with a virtual muon and you'll have two vertices like $h\mu^-\mu^+$. –  Melquíades Mar 26 '14 at 18:29
How do you conserve charge? –  Jon Mar 26 '14 at 18:31
Replace $\gamma$ by $h$ in: en.wikipedia.org/wiki/File:Feynman_EP_Annihilation.svg –  Melquíades Mar 26 '14 at 18:37